JP2018062730A - Polyparaphenylene terephthalamide fiber composite pulp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyparaphenylene terephthalamide fiber composite pulp friendly to environments, having favorable impregnating/infiltrating properties and adhesiveness in relation to thermosetting resins such as phenol resins, and capable of obtaining frictional materials excellent in strength and durability.SOLUTION: Polyparaphenylene terephthalamide fiber composite pulp is in a pulp state obtained by fibrillating, via a mechanical work, a fiber obtained by impregnating/infiltrating, into a polyparaphenylene terephthalamide fiber skeleton whose water content is adjusted within a range of 15-200 wt.%, a curable epoxy compound and, if necessary, a curing agent, further, a compatibilizer.SELECTED DRAWING: None

Description

  The present invention relates to a polyparaphenylene terephthalamide (hereinafter abbreviated as PPTA) fiber composite pulp.

  PPTA pulp is a particle having a length of about 1 to 3 mm in which PPTA fibers are fibrillated. Commercially known Twaron (trade name; manufactured by Teijin Aramid BV), Kevlar (trade name; manufactured by Du Pont), and the like are known. Yes.

  The main use of PPTA pulp is to make a paper after dispersing the pulp in water, impregnate a dried paper with a thermosetting resin such as phenol resin, It is an insulating material.

  For example, in wet multi-plate clutches for automatic transmissions for automobiles, the lubrication characteristics are exhibited by the leaching of lubricating oil retained in the pores in the friction material, so there is highly fibrillated pulp on the surface layer. By doing so, good friction characteristics are exhibited. Further, in the friction material, further improvements in strength, heat resistance, and durability are required in accordance with the trend of higher rotation and higher output of automobile engines.

  By the way, the main production method of PPTA pulp is a method of mechanically fibrillating an aramid polymer molded product (fiber or film) (hereinafter referred to as a mechanical processing method), or a precipitation in which an aramid polymer solution is stirred at high speed. This is a method of introducing into an agent (N-methyl-2-pyrrolidone) (hereinafter referred to as precipitation method). However, since a precipitation agent is used in the precipitation method, it is economically disadvantageous as an industrial production method.

  There are also two machining methods: a method in which dried continuous fibers are cut into short fibers to fibrillate the short fibers (for example, Patent Document 1), and obtained by spinning PPTA solvent solution instead of dried fibers. There is a method (for example, Patent Documents 2 to 5) using a wet yarn.

  Patent Document 1 discloses a method of producing fibrils by spinning and drying to produce cracked long fibers, and applying mechanical shearing force to the short fibers cut from the long fibers. The pulp produced by this method has a problem in terms of strength when it is used as a friction material because it is poor in impregnation / penetration with phenol resin or the like.

  On the other hand, Patent Document 2 discloses a method of exploding wet yarn (moisture content of 5 to 200% by weight) in order to obtain highly fibrillated pulp particles (length: about 0.5 to 3 mm); In a wet yarn (moisture content of 50% by weight or more), after impregnating a foaming agent (azodicarbonamide), it is heated to a temperature higher than the decomposition temperature of the foaming agent, and fibrils are produced by the breaking force from inside the fiber. In Patent Documents 4 to 5, in order to obtain highly fibrillated PPTA pulp, a dispersion in which short fibers cut in a wet state (water content is unknown) is dispersed in water, a refiner or the like is used. A method of using and mechanically fibrillating with high shear is disclosed. However, these PPTA pulps have problems in performance because they are poor in impregnation / penetration and adhesiveness of phenol resin and the like.

  On the other hand, Patent Documents 6 to 7 disclose that PPTA pulp is surface-treated with an epoxy resin by dispersing PPTA pulp in an aqueous epoxy resin emulsion, followed by filtration and dehydration, The surface-treated epoxy resin elutes into water when pulp is made, and the impregnation / penetration of phenol resin is poor, so there is a problem in terms of strength when used as a friction material, and the COD value of papermaking wastewater also increases. There are also environmental issues.

  Another possible method is to fibrillate a fiber (moisture content of 10% by weight or less) obtained by heat-treating a PPTA fiber composite impregnated and impregnated with a curable epoxy compound by machining. However, in this case, since the impregnated epoxy compound is fibrillated after being cured by heat treatment, it is difficult to uniformly impregnate and infiltrate a phenol resin or the like. There are challenges. And since it heat-processes, it becomes economically disadvantageous as an industrial manufacturing method.

Japanese Unexamined Patent Publication No. 63-190087 JP-A-63-135515 JP-A 63-249716 JP-A-6-41298 JP-A-8-337920 JP-A-6-166984 JP-A-7-243175

  An object of the present invention is a polyparaphenylene terephthalamide fiber that is environmentally friendly, has good impregnation / penetration and adhesion of a thermosetting resin such as a phenol resin, and is capable of obtaining a friction material excellent in strength and durability. It is to provide a composite pulp.

  In order to solve the above problems, the present invention takes the following means.

(1) A polyparaphenylene terephthalamide fiber skeleton adjusted to a moisture content of 15 to 200% by weight is infiltrated and impregnated with a curable epoxy compound and, if necessary, a hardener, and further represented by the following general formula (I). It is formed of fibers obtained by impregnating and impregnating the compatibilizer to be combined with the curable epoxy compound in an amount of 0.1 wt% or more and 10.0 wt% or less, and is a fibrillated pulp. Polyparaphenylene terephthalamide fiber composite pulp characterized by
(Chemical formula 1)
R ¹ —O— (AO) n—R ² (I)
(In the formula, R ¹ is an alkyl group having 1 to 10 carbon atoms or an alkenyl group having 1 to 10 carbon atoms, and R ² is a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or the number of carbon atoms. 1 to 5 represents an alkenyl group, A represents an alkylene group having 2 to 4 carbon atoms, and n represents an integer of 1 to 10 representing the average number of added moles of an oxyalkylene group (AO). In (AO)-, the same oxyalkylene group may be added, or two or more oxyalkylene groups may be added.)

(2) The curable epoxy compound is one kind or a mixture of two or more kinds selected from glycerol diglycidyl ether, glycerol triglycidyl ether, sorbitol polyglycidyl ether, and polyglycerol polyglycidyl ether. Polyparaphenylene terephthalamide fiber composite pulp.

(3) The polyparaphenylene terephthalamide fiber composite pulp according to (1) or (2) above, wherein the curable epoxy compound is contained in an uncured state.

(4) Pulp reinforced resin containing the polyparaphenylene terephthalamide fiber composite pulp and resin in any one of said (1)-(3).

  Since the polyparaphenylene terephthalamide fiber composite pulp of the present invention is made from a fiber composite in which a curable epoxy compound is infiltrated and impregnated into the polyparaphenylene terephthalamide fiber skeleton, the curable epoxy compound is infiltrated / impregnated. Compared to unimpregnated pulp, the adhesive strength with thermosetting resin is higher, and the plate obtained by curing the prepreg impregnated with thermosetting resin on the paper-made paper is heat resistant, tensile strength Excellent bending properties. Therefore, it is possible to provide a friction material that has a long life and a large clutch capacity suitable for a clutch plate and a brake plate of a vehicle or an industrial machine, and can cope with high rotation and high output of an automobile engine. Pulp made from a fiber composite in which a curable epoxy compound and a compatibilizing agent are infiltrated and impregnated into a polyparaphenylene terephthalamide fiber skeleton has good water dispersibility and excellent papermaking properties.

  Hereinafter, the polyparaphenylene terephthalamide fiber composite pulp (hereinafter abbreviated as PPTA fiber composite pulp) of the present invention will be described in detail.

  The PPTA fiber composite pulp of the present invention is produced using fibers obtained by impregnating and infiltrating a curable epoxy compound and, if necessary, a curing agent, into a PPTA fiber skeleton adjusted to a moisture content of 15 to 200% by weight. Is done. In the PPTA fiber skeleton, fibers obtained by impregnating and impregnating a compatibilizing agent represented by the following general formula (I) may be used.

  The polyparaphenylene terephthalamide (PPTA) in the present invention is a polymer obtained by polycondensation of terephthalic acid and paraphenylene diamine, and a copolymer obtained by copolymerizing a small amount of dicarboxylic acid and diamine can also be used. The number average molecular weight of the polymer and copolymer is preferably in the range of 20,000 to 25,000.

A typical PPTA fiber is a viscous solution in which PPTA is dissolved in concentrated sulfuric acid, discharged from a spinneret at a shear rate of 25,000 to 50,000 sec ⁻¹ , spun into air, and then spun into water. It is produced by neutralizing with an aqueous sodium hydroxide solution. By drying this spun fiber at 100 to 150 ° C., a PPTA fiber having a moisture content adjusted to 15 to 200% by weight is obtained. If the PPTA fiber has a moisture content of 15% by weight or more, it is in a state before drying containing moisture higher than the equilibrium moisture content, so the crystal size is relatively small and the gap between PPTA fiber crystals is wide. It becomes easy to infiltrate and impregnate the compound and the compatibilizer into the fiber skeleton. Further, when the moisture content is 200% by weight or less, the fiber unwinding and winding operations are easy. The moisture content is preferably 30 to 200% by weight, and more preferably 35 to 70% by weight.

  As the curable epoxy compound to be impregnated and permeated, either an aliphatic epoxy compound or an epoxy compound having an aromatic ring can be used, and these can be used in combination.

  The aliphatic epoxy compound is preferably one or a mixture of two or more selected from glycidyl ether compounds of polyhydric alcohols such as glycerol, sorbitol, and polyglycerol. Examples thereof include glycerol diglycidyl ether, glycerol triglycidyl ether, polyglycerol polyglycidyl ether, sorbitol polyglycidyl ether, trimethylolpropane polyglycidyl ether, pentaerythritol polyglycidyl ether, and the like. Among these compounds, glycerol diglycidyl ether, glycerol triglycidyl ether, sorbitol polyglycidyl ether, and polyglycerol polyglycidyl ether are particularly preferably used.

  The epoxy compound having an aromatic ring is preferably one or a mixture of two or more selected from bisphenol type epoxy resins. For example, bis (4-hydroxyphenyl) methane [bisphenol F], 2,2-bis (4-hydroxyphenyl) propane [bisphenol A], 2,2-bis (3-methyl-4-hydroxyphenyl) propane [bisphenol C] and the like. Among these, glycidyl etherified products of bisphenol A and bisphenol F that are liquid at room temperature are particularly preferably used.

  As the curing agent, an amine compound is preferable, and a tertiary amine compound is particularly preferable. Examples thereof include dimethyloctylamine, dimethyldecylamine, dimethyllaurylamine, and long-chain alkylpolyoxyethylene type tertiary amine obtained by adding ethylene oxide to an aliphatic primary amine.

The compatibilizing agent has an effect of improving the dispersibility of PPTA fiber composite pulp in water when used in combination with a curable epoxy compound, and a glycol ether compound represented by the following general formula (I) is preferably used. . When the carbon number of R ¹ increases, water solubility decreases, so that it becomes difficult to penetrate and impregnate PPTA fibers having a high moisture content, and when n increases, it becomes difficult to penetrate and impregnate PPTA fibers by increasing the molecular weight. The compatibilizer is preferably a hydrophilic compound rather than a curable epoxy compound.
(Chemical formula 2)
R ¹ —O— (AO) n—R ² (I)

In the general formula (I), R ¹ is an alkyl group or alkenyl group having 1 to 10 carbon atoms, preferably 4 to 8 carbon atoms, and R ² is a hydrogen atom or alkyl having 1 to 5 carbon atoms. A group or an alkenyl group having 1 to 5 carbon atoms; Preferably, R ² is a hydrogen atom. A is an alkylene group having 2 to 4 carbon atoms, preferably an alkylene group having 2 to 3 carbon atoms, and n is an integer of 1 to 10 representing the average number of moles added of the oxyalkylene group (AO), preferably Is 2-8. In-(AO)-, the same oxyalkylene group may be added, or two or more oxyalkylene groups may be added.

  Preferable specific examples of the compound represented by the general formula (I) include diethylene glycol monobutyl ether, diethylene glycol mono 2-ethylhexyl ether, dipropylene glycol monobutyl ether, polypropylene glycol (n = 3) glyceryl ether and the like. These glycol ether compounds may be used alone or in appropriate combination of two or more.

  The amount of impregnation of the curable epoxy compound (including the curing agent) and the compatibilizer into the PPTA fiber skeleton is preferably 0.1 to 10.0% by weight, more preferably 0.2 to It is 4.0% by weight, more preferably 0.2 to 2.0% by weight. Here, the “impregnation amount” is a value relative to the fiber weight when the moisture content of the PPTA fiber is converted to 0%. The impregnation amount of only the curable epoxy compound is preferably 0.1 to 5.0% by weight, more preferably 0.2 to 4.0% by weight, and still more preferably 0.2 to 2.0% by weight.

  In the PPTA fiber skeleton, as other components, a smoothing agent such as an oil agent, a penetrating agent such as a nonionic surfactant, a silicone compound, a fluorine compound, and an organic surfactant, as long as the effects of the present invention are not impaired. In addition, a resin modifier such as oxazoline or acid anhydride, a coupling agent such as silane or isocyanate, and the like may be contained.

  The method for applying the curable epoxy compound and the compatibilizer to the PPTA fiber is not particularly limited, and may be a known method such as an immersion oil supply method, a spray oil supply method, a roller oil supply method, or a guide oil supply method using a metering pump. Good. The order in which the curable epoxy compound, the curing agent, and the compatibilizer are added is not particularly limited, and may be applied stepwise or simultaneously. In stepwise application, the curable epoxy compound and the compatibilizer are applied in this order. Is preferable in terms of process and performance.

  After impregnating the curable epoxy compound and the like, the PPTA fiber composite is stored in a room temperature atmosphere until it is machined to allow the curable epoxy compound to penetrate more into the PPTA fiber skeleton. You may go. However, when performing the aging treatment, it is necessary to take measures so that moisture on the surface of the PPTA fiber composite does not evaporate more than necessary in order to efficiently perform fibrillation by machining. Although it does not specifically limit as a method which does not reduce the moisture content of a PPTA fiber composite, The PPTA fiber composite wound up is packaged with a single bag, stored in a humidity-controlled low temperature warehouse, mist-like The method of spraying the mist of this is mentioned. Of these methods, at least one method or a plurality of methods may be used.

  The PPTA fiber composite pulp of the present invention uses a PPTA fiber composite in which a curable epoxy compound is impregnated and impregnated in a polyparaphenylene terephthalamide fiber skeleton adjusted to a moisture content of 15 to 200% by weight, It can be manufactured by applying a conventional machining method. Specifically, the PPTA fiber composite is cut into a length of 1 to 50 mm to form short fibers, and the short fibers are crushed, ground, and subjected to mechanical shearing force such as impact or beating for fibrillation.

  The PPTA fiber composite pulp of the present invention is a highly fibrillated pulp having an average fiber length (weight-weighted average) of about 3 mm or less, and since it has not been heat-treated, it contains a curable epoxy compound in an uncured state. The Compared with a conventional aramid pulp not penetrating / impregnated with a curable epoxy compound, it has a freeness equal to or higher than that of a conventional aramid pulp, and has excellent lubricating oil and powder holding performance.

  In addition, the PPTA fiber composite pulp of the present invention is such that the PPTA fiber composite used as a raw material has a moisture content higher than the equilibrium moisture content, that is, penetrates a curable epoxy compound into a PPTA fiber skeleton having a wide gap between fiber crystals.・ Because it is impregnated, the curable epoxy compound is also attached to the deep part of the fibrils produced by machining, so that the matrix resin such as thermosetting resin or thermoplastic resin can be uniformly penetrated and impregnated. In addition, since the adhesive strength to the matrix resin is high, the matrix resin hardly peels off or drops off.

  The PPTA fiber composite pulp of the present invention is useful as a raw material for para-aramid pulp paper, friction materials, insulating materials, and the like.

  EXAMPLES The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to the examples. In the examples, “%” and “parts” represent “% by weight” and “parts by weight”, respectively, unless otherwise specified.

Example 1
1 kg of PPTA (molecular weight of about 20,000) was dissolved in 4 kg of concentrated sulfuric acid, discharged from a die having 1000 holes with a diameter of 0.1 mm so as to have a shear rate of 30,000 sec ^−1, and spun into water at 4 ° C. Thereafter, neutralization treatment was performed with a 10% aqueous sodium hydroxide solution at 10 ° C. for 15 seconds, followed by heat treatment at 110 ° C. for 15 seconds to produce PPTA fiber having a moisture content of 35% (in terms of 0% moisture content). And a total fineness of 1,670 dtex) was prepared.

  A drug stock solution containing 40 parts of sorbitol polyglycidyl ether as a curable epoxy compound and 60 parts of diethylene glycol mono-2-ethylhexyl ether as a compatibilizing agent is added to this PPTA fiber, and the curable epoxy compound and the compatibilizing agent are added to the PPTA fiber. After impregnating and impregnating, a PPTA fiber composite was produced by winding it on a bobbin. The amount of impregnation (in terms of dry fiber weight) was 0.4% for the curable epoxy compound and 0.6% for the compatibilizer.

  The obtained PPTA fiber composite was cut into 6 mm with a roving cutter. 200 g of the dry weight of this water-containing PPTA fiber composite short fiber was dispersed in 60 kg of ion-exchanged water and fibrillated using a single disc refiner at 3000 rpm to obtain a PPTA fiber composite pulp. The freeness of the pulp measured by the method of JIS P8121-2 was 770 mL.

25 g of the dry weight of the water-containing PPTA fiber composite pulp thus obtained was dispersed in 4 liters of water at 3000 rpm using a pulp disintegrator, and then a # 80 mesh wire mesh was used with a 25 cm square sheet machine. Papermaking was performed according to a conventional method, and then dried to obtain a para-aramid paper having a 25 cm square and a unit weight of 400 g / m ² .

  Next, the obtained para-aramid paper is immersed in a resin solution obtained by diluting a resol-type phenol resin prepolymer with an equal amount of methanol, impregnated with the resin solution, and then dried at 60 ° C. for 20 minutes to obtain a prepreg. It was. The prepreg is further cut into 4 pieces of 12.5 cm square, 1 piece is left as it is, and the other 3 pieces are laminated, treated at 165 ° C. under a pressure of 25 MPa for 10 minutes, cured, and 0.6 mm and 1.8 mm thick 12 pieces. A 5 cm square aramid pulp reinforced phenolic resin plate was prepared.

  A 1BB tensile test piece described in JIS K7162 was cut out from the 0.6 mm plate thus obtained, and a bending test piece described in JIS K7162 was cut out from the 1.8 mm plate.

(Example 2)
A PPTA fiber composite is produced in the same manner as in Example 1, except that a drug stock solution containing 100 parts of glycerol polyglycidyl ether as a curable epoxy compound and 150 parts of diethylene glycol mono-2-ethylhexyl ether as a compatibilizer is used. did. The impregnation amount of the curable epoxy compound (in terms of dry fiber weight) was 1.0%, and the compatibilizer was 1.5%. Using this PPTA fiber composite, a PPTA fiber composite pulp was obtained in the same manner as in Example 1.
A test piece was obtained in the same manner as in Example 1 except that the PPTA fiber composite pulp obtained above was used instead of the PPTA fiber composite pulp obtained in Example 1.

(Comparative Example 1)
Except not adding a curable epoxy compound and a compatibilizer, PPTA fiber having a moisture content of 35% prepared in Example 1 (total fineness of 1,670 dtex when converted to 0% moisture content) was used, and the same as in Example 1. PPTA fiber pulp was obtained by this method.
A test piece was obtained in the same manner as in Example 1 except that the PPTA fiber pulp obtained above was used instead of the PPTA fiber composite pulp obtained in Example 1.

(Comparative Example 2)
The paper made from the 6 mm water-containing PPTA fiber composite short fiber obtained in Example 1 by the same method as in Example 1 without fibrillation with a single disc refiner is weak in paper strength. Cracks occurred and a prepreg could not be created.

(Comparative Example 3)
1 kg of PPTA (molecular weight of about 20,000) was dissolved in 4 kg of concentrated sulfuric acid, discharged from a die having 1000 holes with a diameter of 0.1 mm so as to have a shear rate of 30,000 sec ^−1, and spun into water at 4 ° C. Thereafter, neutralization treatment was performed with a 10% aqueous sodium hydroxide solution at 10 ° C. for 15 seconds, followed by heat treatment at 200 ° C. for 15 seconds to obtain PPTA fibers having a moisture content of 7% (in terms of 0% moisture content). And a total fineness of 1,670 dtex) was prepared.
A curable epoxy and a compatibilizing agent were added to the PPTA fiber in the same manner as in Example 1, and then a PPT fiber composite pulp was obtained in the same manner as in Example 1. Further, a test piece was obtained in the same manner as in Example 1.

<Evaluation test>
(1) Moisture content: The weight of about 5 g of the sample is measured, heat-treated at 300 ° C. for 20 minutes, left at 25 ° C. and 65% RH for 5 minutes, and then weighed again. The moisture content used here is the dry base moisture content obtained by [weight before drying−weight after drying] / [weight after drying].

(2) Freeness: measured according to JIS-P8121-2 (Canadian Standard Freeness or CSF).

(3) Weight average fiber length: measured with HiRes Fiber Quality Analyzer manufactured by Op Test Equipment (CANADA).

(4) Tensile strength, tensile elongation at break, bending strength, flexural modulus;
Using the prepared test piece, the tensile strength and tensile elongation at break were measured by the method of JIS K7162, and the bending strength and the flexural modulus were measured by the method of JIS K7017.

  Table 1 shows the results of evaluation of the pulps and test pieces obtained in Examples 1 and 2 and Comparative Examples 1 and 3 by the above evaluation test.

  From Table 1, the PPTA fiber composite pulp of the present invention was superior to the pulps of Comparative Examples 1 and 3 in that the aramid pulp reinforced phenolic resin was superior in tensile strength, bending strength and bending elastic modulus. It can be seen that the raw material can be excellent in heat resistance, mechanical strength and durability.

  The polyparaphenylene terephthalamide fiber composite pulp of the present invention can be suitably used for aramid paper, friction materials, insulating materials and the like.

Claims (4)

A polyparaphenylene terephthalamide fiber skeleton adjusted to a moisture content of 15 to 200% by weight is impregnated with and impregnated with a curable epoxy compound and, if necessary, a curing agent, and further a phase represented by the following general formula (I): It is formed of fibers formed by impregnating and impregnating a solubilizer in a total amount of 0.1% by weight or more and 10.0% by weight or less as a total amount with the curable epoxy compound, and is characterized by being a fibrillated pulp. Polyparaphenylene terephthalamide fiber composite pulp.
(Chemical formula 1)
R ¹ —O— (AO) n—R ² (I)
(In the formula, R ¹ is an alkyl group having 1 to 10 carbon atoms or an alkenyl group having 1 to 10 carbon atoms, and R ² is a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or the number of carbon atoms. 1 to 5 represents an alkenyl group, A represents an alkylene group having 2 to 4 carbon atoms, and n represents an integer of 1 to 10 representing the average number of added moles of an oxyalkylene group (AO). In (AO)-, the same oxyalkylene group may be added, or two or more oxyalkylene groups may be added.)   The polyparaphenylene according to claim 1, wherein the curable epoxy compound is one kind or a mixture of two or more kinds selected from glycerol diglycidyl ether, glycerol triglycidyl ether, sorbitol polyglycidyl ether, and polyglycerol polyglycidyl ether. Terephthalamide fiber composite pulp.   The polyparaphenylene terephthalamide fiber composite pulp according to claim 1 or 2, wherein the curable epoxy compound is contained in an uncured state.   A pulp reinforced resin comprising the polyparaphenylene terephthalamide fiber composite pulp according to any one of claims 1 to 3 and a resin.